A new study by paleoecologist Margaret Fraiser at the University of Wisconsin, Milwaukee, offers an interesting new theory behind the cause of the Earth's largest extinction: copious carbon-dioxide

When most people hear the phrase "the earth's largest
extinction", they think dinosaurs.

Margaret
Frasier knows better. As a paleoecologist, she knows that the Earth's
largest mass extinction of life occurred at the end of the Permian Period at the end of the Paleozoic Era; 252
million years before the first T-Rex ever walked the earth. The
extinction destroyed the large
land amphibians' dominance of the land, and paved the way for
dinosaurs to emerge as the dominant land species.

University of Wisconsin-Milwaukee professor Margaret Frasier is studying
this extinction avidly, looking for possible details to further our
understandings of what might have caused this landmark event.

Her recent conclusions, published in an Elsevier journal [1]
[2] (PDF)
and detailed in a recent
press release titled "When Bivalves Ruled the World," describe an
Earth with run-away carbon dioxide levels. She concludes that the
Permian-Triassic mass-extinction was caused by toxic, oxygen-less oceans created by too much
atmospheric carbon dioxide (CO2).

The Permian-Triassic extinction event wiped out nearly 70 percent of species on land and 95 percent of
sea species.

“Estimates of the CO2 in the atmosphere then were between six and 10 times
greater than they are today,” Frasier states. The largest continuous
volcanic eruption on Earth – known as the “Siberian Traps” – had been pumping
out CO2 for about a million years prior to the Permian-Triassic mass
extinction.

Her hypothesis is that high CO2 levels at the close of the Permian Period
caused global warming, greatly increasing global temperatures. With no
cold water at the poles, ocean circulation slowed, and the oceans were unable
to mix with the little oxygen left in the air.

She cites a variety of evidence of high CO2 and low ocean oxygen levels in this
fossil record. One piece of evidence is darkened rock from underwater
fossil strata of the time. Darkening in ocean rock of this nature
indicates a low amount of oxygen at the time of formation.

Frasier also collected evidence to support her theory in the form of
bivalve fossils. The only survivors of the extinction were bivalve mollusks
and gastropods -- snails. Only shallow water, tiny, small-shelled
varieties with high metabolisms and a flat shape, which allowed them to spread
out while feeding to extract more oxygen, survived. Deeper water
varieties, where there was less oxygen, and larger shelled varieties, which
needed more oxygen, became extinct, disappearing from the fossil record.

A final piece of evidence cited is the disappearance of the coral reefs.
Coral reefs die if their environment lacks sufficient oxygen.

Comments

Threshold

Username

Password

remember me

This article is over a month old, voting and posting comments is disabled

quote: First of all, a 1% CO2 level doesn't "lead to carbon dioxide poisoning". Our own BREATH has a CO2 level of 4.5%, and even that isn't toxic unless breathed over a lengthy period....which explains why you can breath in and out of a bag for short periods without harm.

quote: A 3% level (the minimum level which can cause any sort of respiratory problems) is a level of 30,000 ppm.